1. Field of Invention
The present invention relates to an automatic cut-sheet feeder for feeding a sheet into an image forming apparatus, for example, a printer or a copying machine. Specifically, the present invention relates to a sheet feeding guide, which can feed a sheet successfully even if the guide is small-sized, and an automatic cut-sheet feeder which can be easily installed on and removed from an image forming apparatus and efficiently received inside the image forming apparatus.
2. Description of Related Art
A conventional automatic cut-sheet feeder retains a stack of plural printing cut-sheets (referred to merely as sheets, hereinafter) which are cut into an A4 size (210.times.297 mm) and successively feeds the sheets, one by one, into an image forming apparatus. Recently, the automatic cut-sheet feeder has been required to be smaller in size to improve space efficiency. In particular, portable automatic cut-sheet feeders need to be made even smaller.
Conventionally, a longitudinal form automatic cut-sheet feeder is known in which a sheet stacking section is attached to an image forming apparatus body upstream, along the sheet feeding direction, so as to be inclined obliquely upward toward the body.
In this conventional feeder, a sheet is supported to stand up obliquely. Thus, an extendible guide which can be received inside the feeder is attached to the automatic cut-sheet feeder in such a manner that the supported sheet will not be bent and its upper edge section will not fall down and backwards.
For an extendible guide is known which is attached to the body of the automatic cut-sheet feeder so as to be able to be received inside the body, and to be able to be pulled out toward the upstream side along the sheet feeding direction and fixed at such a position that the guide is projected from the body.
However, when the automatic cut-sheet feeder is made smaller, the extendible guide which can be received inside the feeder must be made smaller. Such an extendible guide may result in the following inconveniences. That is, even if the extendible guide is extended so that a sheet is set thereon, the extendible guide does not reach the upper section of the sheet and cannot support the upper section. Therefore, that section hangs down off the guide. A rod-like extendible guide may be used which can support only the central section of a sheet; however, the upper and both side sections of the sheet hang down as a result. Therefore, the sheet cannot be fed into the image forming apparatus successfully. The size of the extendible guide, therefore, restricts the size of the sheet which can be applied to the automatic cut-sheet feeder. For this reason, when making an automatic cut-sheet feeder wherein sheets having various sorts of sizes, e.g., A4-, letter- and post card-sizes are used, the plane area of the extendible guide and the size of the feeder automatic cut-sheet body receiving the guide are large, so that such various sheet sizes may be used. These large sizes, however, cause the feeders to be larger in size rather than smaller.
Even if improvements to printers further reduce the size of printers, the automatic cut-sheet feeder needs to have storage space for stacking sheets, i.e., space for a sheet stacking section, a sheet feeding mechanism and the like attached to the feeder. For this reason, and because image forming apparatuses are being made far smaller, the relative imbalance of the size of the image forming apparatus and the size of the sheet feeder attached thereto is compounded. For example, when stacking a large number of sheets onto a longitudinal type automatic cut-sheet feeder and attaching this feeder to a small portable image forming apparatus, stability of the small portable image forming apparatus is largely damaged. The image forming apparatus may tip over because of the weight of the stacked sheets and hanging-down of the upper section of the sheets. In order to maintain stability of the image forming apparatus, the automatic cut-sheet feeder would need to be made small and, consequently, the number of stacked sheets would have to be reduced.
To improve the above-mentioned instability, automatic cut-sheet feeder may be attached to the lower section of an image forming apparatus. In this case, to provide a sheet from the sheet feeder and subsequently feed the sheet into the image forming apparatus, it is necessary to reverse the sheet orientation by 180 degrees. This orientation frequently causes the sheets to jam in the feeder because of the complexity of the image forming apparatus mechanism. Additionally, the orientation causes the stacking capacity to be limited and the print starting position of the sheets to be wrongly positioned, which feeds the sheet obliquely.